<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>数学方程式</title>
        <style type="text/css">
            h3 {
                font-size: 24px;
                color: red;
                text-align: center;
            }

            p {
                text-align: center;
            }
        </style>
    </head>
    <body>
        <h3>数学方程式</h3>
        <hr width="80%" size="2px" color="blue">
        <p>2x<sup>2</sup>+3x=9</p>
        <p>x<sub>1</sub>+x<sub>2</sub>=10</p>
    </body>
</html>